Modem installation for the Samsung Galaxy S2... i9100, i9100M, i9100P & i9100T***, only and no other variant. (If you are unsure of the model of your phone, go to Settings > About phone > Model number) What is a Modem? A modem, (sometimes referred to as a radio or baseband), is a driver that controls the sending and receiving of your mobile Network signals as well as switching between GPRS, 3G and HSDPA. It does not control Wi-Fi or the switchover between mobile signal and Wi-Fi. That is the job of the kernel. To locate your current modem details, go to... Settings > About phone > Baseband version. Modems are not firmware specific.*** You can install any modem for the Galaxy S2 to any firmware, (*** T variants have their own modem version for network compatability), unlike kernels and ROMs. The only thing that I have found is that some, "area", modems do not work well for me in Europe, i.e. DX = Indonesia, Malaysia, Philippines, Singapore, Vietnam or ZS = China, Hong Kong or JP = Arabic, Algeria, Egypt, Iran, Iraq, Kuwait, Morocco, Nigeria, Oman, Pakistan, Saudi Arabia, Syria. For details of country designations, see here. There is no such thing as, "the best modem". It depends entirely on your location, operator and signal strength. The latest modem may not be the best for you, as I have found out. These are the one's that generally work... KE7, KH3, KI3, KI4, KL1, LPS, LPX, NEKF2, NELP2, NELP3 & BVLP7. Why is a good modem important? If your phone has to constanly search for signals and lock on to them it not only gives you a poor call and data quality but also drains your battery. For more information on modems and their uses, see this excellent post by geko95gek over on the xda forum here. Installation instructions (please read carefully and thoroughly) You will need to be rooted, see here, and have ClockWorkMod, (CWM), installed. Before doing anything further you should do a nandroid and Titanium backup. You should also install Root Explorer, or a similar file manager, and use it to navigate to the, "/efs", file in the root directory of the phone and make a copy of this and put it on both your external SD card and PC as its loss or corruption in future could render your phone unusable and require a Samsung repair. These are your, "Get out of jail FREE" cards in case anything goes wrong, now or in the future. (N.B. Please note that a nandroid backup and restore does not include your modem. Therefore, to change your modem you will need to re-flash.) Modem download sources There are a number of places to obtain modems... Modem+RIL CWM Installers by Hawker. As the link suggests, these incorporate the RIL, (Radio Interface Layer), mentioned below. (*** Whilst the modems are interchangeable between GB, ICS and JB, you must use JB RIL's on JB firmware only... GB and ICS RIL's are interchangeable.) Latest i9100 modems Galaxy S 2 Shipped Modem Collection Index of Radios *** T variant modems, see here. Modems that are getting good reviews from Canadian network users are... UGLD3 and XXKG6. Download the .zip version of the modem and place it on your external SD card, safest place, (if you downloaded them using your phone they will be in... "/sdcard/Download"), and then go into CWM Recovery and select, "install zip from sdcard", followed by, "choose .zip from sdcard", and then navigate down the menu until you get to the modem name and install it and then reboot your phone. After installing a new modem, I carry out the following procedure... 1. Settings > Wireless and network > More > Mobile networks > Network operators. 2. Let the screen populate with all the available carriers. 3. Select a carrier that is not your own. You will be told, after trying to connect, not allowed or No way Jose. 4. Repeat this with one or two other non carriers. 5. Finally, select your own carrier, Automatic, and reconnect your phone again. This procedure should ensure that your phone locks on to the strongest signal for your carrier. I normally give a modem 1 or 2 days to, "bed", in before deciding if it is any good or not. As well as testing it in various locations and different times of day. App's for modems GetRIL from the Play Store, attempts to match RIL, (Radio Interface Layer), with your modem for a more efficient operation. Network Signal Info free from the Play Store. Very useful for testing, "most", modems on network and Wi-Fi signals. However, it does sometimes have a problem with the SGSII in getting a reading other than -85dBm on certain modems. Speedtest.net free from the Play Store. Great app for testing your download and upload speeds. (Whilst I have taken every care in compiling this guide, I cannot be held responsible for any damage that may occur through its use and the decision to use this guide lies with you, the owner. This guide is written solely for, and on behalf of, Android Forums and may not be reproduced, in part or whole, without permission) ironass motto... "Flash in haste... repent at leisure"